Short-period Rayleigh wave group and phase velocities of the Reno-Truckee Meadows basin from ambient seismic noise
Abstract
The Reno-Truckee Meadows basin in western Nevada experiences high seismicity rates, exposing the population to significant seismic hazards. We expect that earthquake ground-motions are amplified in this basin, however current-generation ground motion prediction equations were developed with few measurements from sensors sited within deep sedimentary basins. Improved estimates of ground motion require detailed knowledge of 3D basin structure and the use of 3D numerical ground motion simulations. The main goal of this work is to develop a 3D shear wave velocity model of the near surface (depths less than 2 km) of the Reno basin using ambient seismic noise analyses. In order to investigate shallow structures in the Reno basin, we deployed 12 broadband seismic stations, with average station spacings ranging 2-3 km, and recorded continuous ground velocities between late February and March 2011. We calculate interstation Green's functions from ambient seismic noise and report on the progress of our analyses here. We cross-correlate vertical component time series to recover 91 empirical Green's functions (EGFs). EGFs contain surface wave energy in 0.5-5 s period band, with inter-station distances ranging from 2-18 km. From the frequency content of the cross-correlations, we expect to resolve shear wave velocity structures above 2 km. Based on the asymmetry of the EGFs, ambient seismic noise sources 2-3 s period appear to locate west of the array, and perhaps originate near the coastlines; shorter period signals show greater symmetry in the EGFs and may result from local, possibility cultural, sources. However, further work will be required to definitively identify the locations of the noise sources. We measure surface wave group and phase velocities by frequency-time analyses and find clear agreements between the lateral distributions of surface wave speeds and the inferred basin depths. Future work will focus on inversion of the inter-station surface wave dispersion measurements for lateral distribution of surface wave speeds, and inversion for 3D shear wave velocity structure. Most previous ambient noise tomography studies obtain group and phase surface velocity dispersion measurements at periods T > 5-10 s (i.e. Shapiro and Campillo (2004); Yao et al., (2006); Yang et al. (2008)), which are longer that those used in this study. As a result, a secondary goal of this study is to investigate the ability of a small, temporary, broadband seismic array to characterize the shallow subsurface at depths beyond those retrieved by standard geotechnical methods.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.S43B2542N
- Keywords:
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- 7200 SEISMOLOGY;
- 7205 SEISMOLOGY Continental crust